This didn't have to happen." So said Cho Seung-Hui in his final message, which he mailed to NBC.

In the aftermath of any tragedy, personal or collective, the human mind retraces steps and looks at what might have kept the tragedy from happening.

In the case of Monday's massacre at Virginia Tech, the first look has been at our insane gun laws -- and rightly so.

The fact that a clearly disturbed individual like Cho, a young man who had been found to be "mentally ill" and potentially dangerous by a Virginia court, could so easily -- and legally -- purchase the semiautomatic weapons he used on his rampage should make even the most ardent fan of the Second Amendment take pause (and the rest of us pull our hair out).

We urgently need a national debate about guns. But we also urgently need a national debate about the epidemic of mood-altering drugs being prescribed to young Americans.

I'll take my teachable moments wherever I can find them. And Virginia Tech has the potential to be one of them.

Reports that Cho had been taking antidepressants once again turn the spotlight on the uneasy question of what role these powerful medications might have played in yet another campus massacre.

It's the same bloody-morning-after question I've been asking since 1998, when we learned 15-year old Oregon school shooter Kip Kinkel, who opened fire in his school cafeteria, had been on Prozac. Nearly ten years -- and numerous school-shooters-on-prescription-meds -- later, we're still waiting for answers.

Now let me make it perfectly clear that I am NOT saying that antidepressants are what caused Cho to go off the deep end and kill 32 people and then himself (indeed, school and law enforcement officials haven't yet disclosed what specific meds were found among his effects). And I'm NOT saying that there aren't thousands of people who benefit from such medication. What I AM saying is that it is absurd -- and incredibly irresponsible -- for our leaders, and our culture, not to be fully investigating the correlation between antidepressants and manic/suicidal behavior.

Despite disturbing evidence of drug-induced reactions, the number of children being given mood-altering drugs continues to soar. America now has over 8 million kids on such drugs.

Eli Lilly, the maker of Prozac, has vehemently denied numerous claims that the drug causes violent or suicidal reactions. But the company's own documents admit that "nervousness, anxiety, insomnia, inner restlessness (akathisia), suicidal thoughts, self mutilation, manic behavior" are among the "usual adverse effects" of the medication. And a clinical trial found that Prozac caused mania in 6 percent of the children studied.

Can there be any doubt that Cho was exhibiting many of these adverse effects during his reign of terror in Blacksburg? His rambling, multi-media diatribe seems like a textbook example of manic behavior. The question is, was his manic behavior purely the result of a sick mind or was drug-induced psychosis part of the toxic psychological mix?

We don't know. But we do know that one school shooter after another was on prescription drugs. Kip Kinkel was taking Prozac. Columbine killer Eric Harris was taking Luvox. Red Lake Indian Reservation shooter Jeff Weise was taking Prozac. James Wilson, who shot 2 elementary school kids in Greenwood, South Carolina, was taking anti-depressants. Conyers, Georgia school shooter T.J. Solomon was on ritalin. Is this just a coincidence?

Again, we don't know. But here are some of the questions we need answers to:

1. It's been reported by the New York Times that Cho was on prescription medications. Which ones? Who prescribed them? How long had he been taking them?

2. If the drugs were prescribed when he was admitted to the New River Community Services center near Virginia Tech in December 2005, which doctor kept refilling his prescriptions? And what was the diagnosis?

3. What kind of medical and/or psychological follow-up was there? Or was Cho one of the many people put on antidepressants without a thorough and ongoing monitoring of the results and side effects?

America's blogs and op-ed pages are teeming with discussions about the impact Monday's carnage will have on America's relationship with guns. It's well-past time to also embark on a national discussion about the potentially deadly side effects of our pill-for-every-ill culture.

And for the discussion to really begin, we need answers to all these questions. The lives of our children could be riding on the answers.

In December 2005 — more than a year before Monday's mass shootings — a district court in Montgomery County, Va., ruled that Cho presented "an imminent danger to self or others." That was the necessary criterion for a detention order, so that Cho, who had been accused of stalking by two female schoolmates, could be evaluated by a state doctor and ordered to undergo outpatient care.

According to the "Temporary Detention Order" obtained by ABC News, psychologist Roy Crouse found Cho's "affect is flat and mood is depressed.

"He denies suicidal ideation. He does not acknowledge symptoms of a thought disorder," Dr. Crouse wrote. "His insight and judgment are normal."

That information came to light two days after Cho, a Virginia Tech senior, killed 32 people and then himself in a shooting rampage on the university's campus.

'An Imminent Danger to Himself'

The evaluation came from a psychiatric hospital near Virginia Tech, where Cho was taken by police in December 2005, after two female schoolmates said they received threatening messages from him, and police and school officials became concerned that he might be suicidal.

After Dr. Crouse's psychological evaluation of Cho, Special Justice Paul M. Barnett certified the finding, ordering followup treatment on an outpatient basis.

On the form, a box is checked, showing that Cho "presents an imminent danger to himself as a result of mental illness."

Immediately below it was another box that is not checked: "Presents an imminent danger to others as a result of mental illness."

Cho was taken to Carilion St. Albans Behavioral Health Center in Radford, Va., a private facility that can take 162 inpatients, according to court documents.